Tracing board



March 3, 1970 M. PADOWICZ TRACING BOARD Filed Aug. 5, 1968 Miran Padowicz INVENTOR BY Mg Attorney United States Patent 3,497,970 TRACING BOARD Miron Padowicz, Kotthusser Domm 70/1, Berlin 61, Germany Continuation-impart of application Ser. No. 515,570, Dec. 22, 1965. This application Aug. 5, 1968, Ser. No. 750,296 Claims priority, application Germany, Dec. 24, 1964,

US. Cl. 3566 7 Claims ABSTRACT OF THE DISCLOSURE Tracing board in which a base is overlain by a flattened bag of flexible and preferably transparent material filled with a deformable mass of shape-retentive character, i.e. a mixture of mineral oil or low-viscosity, high-penetration grease with a thickener constituted by a wax, a metal soap or a high-viscosity mineral-oil grease in the presence of a small proportion of a coloring agent; the oil or lowviscosity grease preferably represents between about 20% and 50%, by weight, of the thickener.

mation of various configurations in plastic relief against a contrasting background.

Another object of this invention is to provide a tracing board of this type in which the background may be readily replaced by one having a different color or pattern.

Thus, my invention aims at providing a simple and inexpensive device which teachers, students, artists and other persons may use for creative work, relaxation or communication.

In accordance with this invention I provide a tracing board which comprises a flattened bag of flexible and preferably transparent material, advantageously a thermoplastic substance such as polyvinylchloride or polyethylene, filled with a permanently fluid viscous mass of opaque coloration, this mass forming a moldable body which may also act as a displaceable masking agent on a contrasting background provided by a base underlying the transparent bag.

It has been found important, in order to have the desired plasticity and shape-retaining ability, that the mass within the bag consist predominantly of a grease mixture of at least two components, one of which is a low-viscosity, high flowability component and is present in an amount ranging between 15 and 50% by weight, the other being a thickening or high-viscosity, low-flowability component. The grease mixture may constitute up to 96% of the composition. When the low-viscosity component is a mineral oil, it may be present in a proportion of 16 to 24% by weight of the composition so that it preferably accounts for about one-fifth of the total mass, the balance being a thixotropic thickener, such as a wax or a metal soap, and a colorant such as carbon black present in a minor proportion of or more as indicated below.

Alternatively, the low-viscosity substance may be a lime-based mineral-oil grease while the high-viscosity substance is a chemically similar lime-based mineral-oil grease of lower fiowability. In this case, the two components may be present in substantially equal parts by weight.

When reference is made herein to the advantageous combination of a mineral oil and a thickener, it will be apparent that the thickener may also be a product chemically similar to the oil. Thus, I have found that a mixture, in the proportions given or up to equipoise (50%- 50% of two greases having low penetration value (e.g. 220 to 250 under ASTM standard D217 or German Industrial Standard DIN 51804) and high penetration value (e.g. 265 to 295 under ASTM D217), respectively, may be used as a grease mixture, in an amount ranging up to about 96% by weight, in the moldable and shapable composition together with the pigment (up to 5% by weight).

With the aid of a simple tool, or even by the fingernails of the user, the front wall of the bag may be pressed against the rear wall at selected locations whereby the viscous filling is squeezed aside and the underlying background is directly exposed to view. By the same type of operation it is also possible to concentrate all or part of the viscous mass at a selected location so as to create a bulge in the bag which can then be modeled into a three-dimensional structure rising from the base. In order to facilitate interchangeability of background, the base-or part thereof-may be removably held in a frame engaging the bag. In particular, this base may consist of a plate-shaped support rigid with the frame and an adjoining sheet which can be withdrawn through an open side of the frame and whose surface confronting the bag may bear a color or pattern different from that of some other background-forming sheet adapted to be substituted therefor.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a perspective view (parts broken away) of a tracing board according to the invention; and

FIG. 2 is a cross-sectional view taken on the line 11-11 of FIG. 1.

The device shown in the drawing comprises a frame 6 which accommodates a rigid support plate 1, a background-forming sheet 2 removably fitted in front of plate 1 and shown in FIG. 1 in a partly withdrawn position, at antifriction layer 9 of transparent sheet material disposec' forwardly of the base 1, 2, and a flattened bag 3 of flexible transparent thermoplastic material extending across the front of the frame. Bag 3, whose rear and front walls have been designed 3', 3" in FIG. 2, is filled with a viscous greasy mass 4 of dark color, specifically a mixture 01 mineral oil with a metal soap and/or a wax to which z carbonaceous pigment has been added in a suitable blend er. With the oil present in the proportions indicated above the bag is readily deformable but of surprising three dimensional stability at room temperatures.

As indicated in FIG. 1, a simple T-shaped tool 7 witl broad and narrow ends may be manually displaced across the front wall 3" of bag 3 to create a bright trace 7' by displacing the mass 4 from the region onto which pressure has been exerted by the tool; one of the pointed end: of the tool may be similarly used to produce a much nar rower trace. The thin and substantially completely trans parent grease film remaining between the walls 3, 3 causes the walls to adhere to each other so as to retair the shape last given to the bag by the tool 7. It may be noted in this connection that the walls 3', 3" need no necessarily consist of the same transparent material.

As has been indicated in dot-dash lines in FIG. 2, tht mass 4 may be selectively accumulated in some area l1( give rise to a bulge 3a in the front wall 3", this bulg having of course the same dark appearance as the re manider of the bag at any point where the two walls 3' 3" have not been forced into adhesive contact with each other. Bulge 3a may be sculptured into any desired protruding shape and, of course, may also be subdivided into several smaller bulges separated by flattened bag portions through which the light background is visible.

The sheet 2 may be white, colored or variegated and, if desired, may be replaced by some other sheet of different color and/or pattern; a tab 2 facilitates its withdrawal from the frame 6.

The antifriction layer 9 may be connected with the frame 6 by heat-sealing, cementing, clamping or other means. Its front surface, contacting the rear wall 3' of bag 3, may be suitably greased to facilitate contractions or expansions of the bag and to relieve local stresses within the wall 3'. In a simplified device, however, layer 9 could be omitted and bag 3 may rest directly against the base 1, 2. Furthermore, the desired background could also be provided directly by the front surface of support plate 1, with omission of the sheet 2.

The mass 4 should be reasonably stable over a substantial temperature range, e.g. from 20 C. to +50 C. It may be composed, for example, of 75% (by weight) of ceresin wax or calcium stearate, 20% of mineral oil and 5% of carbon black. If greater viscosity is preferred, the proportion of mineral oil should be reduced, particularly at higher ambient temperatures; in cooler surroundings it may be somewhat increased. The range of 16 to 24% of the total, by weight, or between about 20 and 30% of the thixotropic additive, has been found suitable under virtually all practical conditions of use. Naturally, the proportion of carbon black or other colorant is not critical for the shape retentiveness of the mixture; if opacity is not a factor, as when the bag 3 is not transparent, the pigment may be entirely omitted, a reasonable upper limit being about half the weight of the oil.

Another example of amixture of great stability and shape retentiveness is a mixture of equal parts by Weight (50%-50%) of two lime-based mineral oil greases having Work penetrations at 25 C. of 265-295 and 220-250, respectively, as determined by ASTM. standard D217 and German Industrial Standard DIN 51804. The first grease has a sulfate-ash content of 4.2% and a water content of 0.6-0.9% whereas the sulfate-ash content of the second grease is 4.6% and the water content 0.7-1%. The chloride content of both greases is less than 0.01% and the neutralization number is 0.2-0.6 mg. KOH/ g.

32 kg. of this grease mixture is blended with 1.2 kg. of

graphite and 280 g. of carbon black to form the plastic mass.

I claim.

1. A tracing board comprising a flat base forming a distinctive background, a flattened bag of flexible material overlying said base, and an antifriction layer of trans parent sheet material interposed between said bag and said base, said bag being filled with a permanently deformable mass of shape-retaining character at room temperature and selectively displaceable by the exertion of pressure upon an exposed wall portion of said bag, said mass being essentially a greasy mixture of a first component of low viscosity with a second component of high viscosity, said first component being present in an amount of 15 to 50% by weight of said mass, said greasy mixture constituting up to by weight of the mass, a frame securing said bag to said base, said base including a support permanently fixed to said frame and a backgroundforming sheet removably interposed between said support and said bag.

2. A board as defined in claim 1 wherein said flexible material is a transparent thermoplastic substance.

3. A board as defined in claim 2 wherein said thermoplastic substance is polyvinylchloride or polyethylene.

4. A board as defined in claim 2 wherein said mass includes a carbonaceous pigment.

5. A board as defined in claim 4 wherein said pigment is present in an amount of about 5% by weight of said mass.

6. A board as defined in claim 5 wherein said mass comprises a grease mixture making up the balance of said mass, said grease mixture consisting of substantially equal parts by weight of two lime-based mineral oil greases, one of said greases having a work penetration of 220 to 250 at 25 C. under ASTM Standard D217, and the other of said greases having a work penetration of 265 to 295 at 25 C. under ASTM Standard D217.

7. A board as defined in claim 5 wherein said mass includes between 16 and 24% by weight of mineral oil and a thixotropic thickener selected from the group which consists of calcium stearate and ceresin wax making up the balance of said mass.

References Cited UNITED STATES PATENTS 2,487,690 11/ 1949 Black et al. 3,279,100 10/ 1966 Knott.

FOREIGN PATENTS 689,870 '6/ 1964 Canada. 343,742 2/1931 Great Britain.

EUGENE R. CAPOZIO, Primary Examiner HARLAND S. SKOGQUIST, Assistant Examiner US. Cl. X.R-. 1615 

